This invention relates to the field of medical interventional diagnostic devices. In particular, this invention provides a system and method for the detection, localization, and characterization of occlusions and aneurysms in blood or other body vessels and to the evaluation of clinical treatment success (e.g. tracking sufficient opening of the occlusion or malpositioning of a stent). Also, this invention provides a method and system for vessel wall characterization and diagnosis of the vascular bed.
Vascular diseases are often manifested by reduced blood flow due to atherosclerotic occlusion of vessels. For example, occlusion of the coronary arteries supplying blood to the heart muscle is a major cause of heart disease. Invasive procedures for relieving arterial blockage such as bypass surgery and balloon dilatation with a catheter are currently performed relying on estimates of the occlusion characteristics and the blood flow through the occluded artery. These estimates are based on measurements of occlusion size and/or blood flow or blood pressure before and after the stenosis. Unfortunately, current methods of occlusion size and blood flow measurement have low resolution, are inaccurate, are time consuming, require expertise in the interpretation of the results and are expensive. Thus, decisions on whether or not to use any of the blockage relieving methods and which of the methods should be used are often based on partial information. The evaluation of therapeutic success is also problematic, where both occlusion opening and stent position must be evaluated.
Typically, the physician first selects the appropriate treatment method from among medication therapy, transcatheter cardiovascular therapeutics (TCT), coronary artery bypass grafting (CABO), or non-treatment. Atherosclerotic lesions may have different characteristics. Some lesions exhibit a variable degree of calcification while others have a fatty or thrombotic nature. Lesion characteristics together with vessel condition distal to the lesion and the vascular bed (VB) condition are the major factors for determining the therapeutic procedure needed. Recently, increasing numbers of patients are directed toward TCT. TCT starts with an interventional diagnosis procedure (most commonly used is angiography), followed by the treatment of the patient with medication therapy, CABG or continuation of the TCT procedure with adequate interventional treatment. TCT final stage include diagnosis tools, for the evaluation of treatment success.
Numerous methods are currently available for treating various lesion types. Some of these methods are given herein below, sequenced from xe2x80x9csofterxe2x80x9d to xe2x80x9cheavierxe2x80x9d, relating to their ability to open calcified lesions; percutaneous transluminal angioplasty (PTCA), xe2x80x9cCutting balloonxe2x80x9d angioplasty, directional coronary atherectomy (DCA), rotational coronary atherectomy (RCA), Ultrasonic breaking catheter angioplasty, transluminal extraction catheter (TEC) atherectomy, Rotablator atherectomy, and excimer laser angioplasty (ELCA). Often, stents are placed within the lesion so as to prevent re-closure of the vessel (also known as recoil). If the stent is malpositioned ,it disrupts the flow and may initiate restenosis.
Lesion characteristics, together with vessel condition proximal and distal to the lesion and vascular bed condition are used to determine the medically and economically optimal treatment method or combination of methods of choice. The main geometrical parameter of the lesion is stenosis severity As/Ao. Here is the minimal open cross-sectional area of the stenosis and AO is the nominal cross-sectional area of the unobstructed vessel The second parameter is the stenosis length. Another clinically important lesion characteristic is the lesion calcification level, A non-calcified arterial wall or lesion is usually a non-chronic, fat based plaque that may be treated by medication therapy, or by the softer, less expensive, PTCA method. Heavily calcified lesion typically requires harder methods, such as ELCA .The calcification level influences the decision whether to use a dilatation balloon prior to stenting. For example, in cases of very soft lesions, the physician may elect not to use a dilatation balloon prior to stenting. In cases where the degree of calcification dictate the use of such a balloon, the vessel wall calcification level influences the optimal inflation pressure of the dilatation balloon. Chapter 12 entitled xe2x80x9cCALCIFIED LESIONSxe2x80x9d of the book xe2x80x9cThe New Manual of Interventional Cardiologyxe2x80x9d (Eds Mark Freed, Cindy Grines and Robert D. Safian, Physicians"" Press, Birmingham, Mich., 1996, pp. 251-261), discusses various methods for the assessment of the degree of vessel wall calcification and their importance in selecting a treatment method.
Decisions about post dilatation processes such as stent deployment for preventing wall recoil and restenosis, or radiation exposure for preventing restenosis caused by cell proliferation, are also influenced by vessel wall and lesion characteristics. Unfortunately, while lesion geometry is evaluated by angiography, qualitative coronary angiography (QCA), or by intravascular ultrasound (IVUS), accurate information regarding the vessel wall structure and composition and the degree of calcification of the lesion and of the vessel wall sections neighboring the lesion is frequently unavailable due to the expenses involved in obtaining this information. Angiography has been the main diagnostic tool in the oath lab. The physician interprets angiographical images in the following sequence: identification and location of the severe lesions, evaluation of the occlusion level (in diameter percentage of the occluded portion), qualitative estimation of the perfusion according to xe2x80x9cthrombolysis in myocardial infarctionxe2x80x9d (TIMI) grades, determined according to the contrast material appearance. TIMI grades 0,1,2,3 represent no perfusion, minimal perfusion, partial perfusion and complete perfusion, respectively.
Among the more sophisticated diagnostic tools are qualitative coronary angiography (QCA), intravascular ultrasound (IVUS), intravascular Doppler velocity sensor (IDVS) and intravascular pressure sensor (IPS). QCA calculates geometrical properties from angiographic images, in image zones that are chosen by the physician. IVUS provides accurate geometrical data regarding cross section area and accurate information regarding the vessel wall structure and composition. Physiological parameters have been introduced in order to help the clinician to elect the appropriate clinical solution. IDVS provides velocity measurements, enabling discriminating various degrees of occlusion according to coronary flow reserve (CFR) criteria. IDVS suffers from inaccuracy problems resulting from positioning errors within the vessel.
IPS provides pressure measurements enabling discriminating various degrees of occlusion according to the FFR (fractional flow reserve) criteria and according to the pressure drop across the stenosis. While measuring the pressure based parameters, the transducer should cross the stenosis and measure pressure downstream of the stenosis The need to cross the stenosis prevents the use of this parameters for purely diagnostic purposes, since stenosis crossing is considered of high risk and therefore, unjustified for diagnostic purposes.
Angiography and the sophisticated techniques discussed above may be employed prior to and after therapeutic procedure (the last for the evaluation of the results and decision about correcting actions). Unfortunately, the above discussed sophisticated methods are rarely used due to their high price, operation complexity and the prevailing feeling among physicians that while they provide more accurate information, this information usually does not contribute to clinical decisions.
Pressure, flow and geometry are three variables often measured in the cardiovascular system. Recent progress in invasive probe miniaturization, improvements of the frequency response of probe sensors and computerized processing have opened a whole new range of intravascular pressure and flow measurements and analysis that have been previously impossible to perform. A method for determination of the reflection sites in the arterial system was suggested by Pythoud, F. Stergiopulos, N. Westerhof, N. and Meister, J. J. in xe2x80x9cMethod for determining distributions of reflection sites in the arterial systemxe2x80x9d in Am. J. Physiol 271 (1996). They studied reflections of pressure and flow waves generated by the beating heart, in the arterial ti-ee using simultaneous pressure and flow measurements. The low (up to 10 Hz) bandwidth of the pressure and flow signals prevent accurate determination of the distance to reflection site by these authors. Correct determination of reflection source location requires accurate estimation of the pressure wave velocity (PWV) in the vessels under consideration and under the specific pressure signal, in contrast with literature data that is based on healthy arteries under beating heart pulses. All known methods for PWV measurement, used two, three or more simultaneous measurements, which prove impractical considering clinically available tools and methods. Further, various attempts have been done to analyze pressure and flow wave changes caused by occluded sites. Harmonic distortions, changes in pressure wave velocity phase velocity, wave attenuation, and additional reflection sites within the arterial tree prevent successful interpretation and implementation within clinical methods or tools.
The invention discloses a method and devices for detection, localization and characterization of occlusions, aneurysms, wall characteristics and vascular bed by introducing an artificial pressure or flow excitation signal (a single signal or multiple signals) into the blood vessel (or in any other tubular flowing fluid conduits), measurement and analysis of the pressure and or flow. The invention provides a method and devices for detection and characterization of partial or total occlusion or aneurysm in blood vessels or in other tubular flowing fluid conduits within a body, such as urine flow in the urethra.
This invention also provides a method and system for measuring blood vessel wall displacement parameters at two points with known distance between them, instead of measuring excited pressure signal. Measurements are by means of non invasive ultrasound. In one embodiment, the measured parameter is vessel diameter. In another embodiment, the measured parameter is vessel cross section area. Such measurements may be are performed by means of Magnetic Motion Sensor. In one embodiment a healthy artery diameter is determined.
In another embodiment, the method and system determine stenosis location, length, inner diameter and shape using correlation between measured exited pressure signal along blood vessel and stenosis characterization. In another embodiment, the method and system determine stenosis location, length, inner diameter and shape using correlation between calculated exited pressure gradient along blood vessel and stenosis characterization. In another embodiment, the method and system determine stenosis location, length, inner diameter and shape using correlation between calculated square root of exited pressure gradient along blood vessel and stenosis characterization.
The methods and systems for determining healthy artery diameter proximal to stenosis using known using catheter properties (cross section area PWV inside the catheter), PWV inside blood vessel and measured maximal exited pressure signal inside the catheter and inside the blood vessel.
In another embodiment, a multi-pressure number of sensors located along the blood vessel measure propagation of the excited signal. In one embodiment the sensors are movable. In another embodiment the sensors are not movable. In another embodiment, the exciter introduces different signal shapes so as to provide better accuracy of measurements.
This invention provides a method for determining pressure wave velocity (PWV) and reflection site parameters comprising the steps of estimation based on two-point pressure measurement carried out inside of an artery. As provided herein the pressure is measured by sensors, either simultaneously by two pressure sensors or in different time by single sensor. Further, in the case of the simultaneously pressure measurement two pressure sensors are placed throw fixed distance d measuring pressure versus time. Since the time measuring interval. As described herein, in the single sensor case the pressure is first measured in point a (upstream) and after thatxe2x80x94in point b (downstream). The distance d between these points is known. The reflection site (in instance stenosis) is placed in point C Time synchronization of the different measurements is performed using an external excitation short duration pulse as reference. Other method that can also be used for synchronizing such as synchronization by a hart beat signal. After synchronization the time measuring interval and distance between the two pressure sensors are known and then PWV can be calculated.
This invention provides an apparatus for the excitation of the pressure waves inside the tube (catheter) (FIG. 43). The apparatus comprises a hammer (95) and conical chamber (96). Low voltage is applied to the solenoid that pushes the weight (hammer). This weight strokes the membrane (97) of the conical chamber thus initiating a short pressure pulse. The opening of the cone is connected to a catheter (98). In the initial state the chamber and the catheter are filled with the fluid. The movement of the membrane is allowed only in one direction, so only positive pressure pulse is produced. Membrane came back to the initial position by the effect of returning spring. Displacement of the membrane and pressure wave generation could be achieved as well by using an actuator based on piezoelement or other device.
This invention provides a method of determining the geometrical shape of the stenosis. Such determination as provided for herein is determined by comparing the pressure signal proximal to the stenosis to the pressure signal distal to the stenosis so as determine the geometrical shape of the stenosis. In another embodiment the reflection method as disclosed herein is determined and then based on the reflection the geometrical shape of the stenosis is determined.
This invention provides a method and devices may also serve for evaluating the success of medical treatment. For example tracing sufficient opening of the occlusion or malpositioning of a stent. It may also serve for the characterization of vascular bed, downstream the vessel.
The present invention includes also a method for further analysis of the response to the excitation signal yielding a quantitative determination of elastic properties of blood vessel walls for characterizing, inter alia, the distensibility and the compliance of lesioned and non-lesioned parts of blood vessels. The derived elastic properties may be further used to determine the degree of calcification of lesioned and non-lesioned parts of blood vessels.
This invention provides an apparatus for detecting, locating and characterizing changes in a tubular conduit system within a living body for transferring fluids, said apparatus comprising: a signal generator configured to transmit into said tubular conduit a probe signal that changes in response to encountering changes in said tubular conduit system; a signal sensor operative to receive said probe signal following transmission into said tubular conduit system; a processor unit operatively connected to said signal sensor; a program for controlling the processor unit; said processor unlit operative with said program to receive said probe signal following, transmission through said tubular conduit system:identify changes in said probe signal; detect characteristics of said tubular conduit system, said characteristics of said tubular conduit system being derived from changes in said probe signal; and recognize and assign a label said characteristic of said tubular conduit said system.
This invention provides a processor apparatus for detecting, locating and characterizing changes in a tubular conduit system within a living body for transferring fluids for use with a signal generator configured to transmit into said tubular conduit a probe signal that changes in response to encountering changes in said tubular conduit system and a signal sensor operative to receive said probe signal following transmission into said tubular conduit system, said processor apparatus comprising: a processor unit operatively connected to said signal sensor; a program for controlling the processor unit; said processor unit operative with said program to receive said probe signal following transmission trough said tubular conduit system; identify changes in said probe signal; detect characteristics of said tubular conduit system, said characteristics of said tubular conduit system being derived from changes in said probe signal; recognize and assign a label said characteristic of said tubular conduit said system; and ascertain and assign a value corresponding to the location and size of said characteristic of said tabular conduit.
This invention provides a method for using a computer to detect, locate and characterize changes in a tubular conduit system within a living body for transferring fluids wherein said computer is operatively connected to a signal generator configured to transmit into said tubular conduit a probe signal that changes in response to encountering changes in said tubular conduit system and a signal sensor operative to receive said probe signal following transmission into said tubular conduit system, said method comprising the steps of: receiving said probe signal following transmission through said tubular conduit system: identify changes in said probe signal; detecting characteristics of said tubular conduit system, said characteristics of said tubular conduit system being derived from changes in said probe signal; and recognizing and assigning a label said characteristic of said tubular conduit said system.
Lastly, the present invention includes also a method for further analysis of the response to the excitation signal yielding a quantitative determination of elastic properties of blood vessel walls for characterizing, inter alia, the distensibility and the compliance of lesioned and non-lesioned parts of blood vessels. The derived elastic properties may be further used to determine the degree of calcification of lesioned and non-lesioned parts of blood vessels.